Technical Field
The present disclosure generally relates to field effect transistor (FET) structures with wrap-around gates and, in particular, to a high performance multi-channel gate-all-around FET.
Description of the Related Art
Conventional integrated circuits incorporate 2-D planar field effect transistors (FETs) in which current flows through a semiconducting channel between a source and a drain, in response to a voltage applied to a control gate. To provide better control of the current flow, 3D transistors have also been developed. A 3D transistor structure is shown and described below in comparison with a traditional 2-D planar transistor. A 3D transistor is an electronic switching device in which the planar semiconducting channel of a traditional FET is replaced by a semiconducting fin that extends outward, normal to the substrate surface. In such a device, the gate, which controls current flow in the fin, wraps around three sides of the fin so as to influence the current flow from three surfaces instead of one. The improved control achieved with a 3D design results in faster switching performance and reduced current leakage, which allows 3D transistors to consume less power so that they can operate at a lower supply voltage. Intel described this type of transistor in an announcement on May 4, 2011, calling it by various names including a 3D transistor, a 3-D Tri-Gate transistor, or a FinFET. (See, for example, the article titled “How Intel's 3D tech redefines the transistor” located on the Internet at http://news.cnet.com/8301-13924_3-20059431-64.html; see also U.S. Patent Application Publication No. 2009/0090976 to Kavalieros et al., published on Apr. 9, 2009; U.S. Pat. No. 8,120,073 to Rakshit et al.; U.S. Pat. No. 7,973,389 to Rios et al.; U.S. Pat. No. 7,456,476 to Hareland et al.; and U.S. Pat. No. 7,427,794 to Chau et al.) FinFET transistors are now well known in the art and are used throughout the semiconductor industry to provide high speed and high reliability transistor performance for devices having gate dimensions smaller than about 25 nm.
More recently, another type of 3D transistor has been developed for technology nodes below 10 nm, referred to as a gate-all-around (GAA) FET, in which the gate surrounds all four sides of the current channel so as to influence the current flow from every direction, and reduce short channel effects (SCE). Instead of providing a fin, in a GAA FET the current channel takes the form of one or more silicon nanowires coupling the source and drain regions.